Shelf surfaces must be created to give somewhere for the synthetic canvases to sit. For this, a new empty layer is created. The polygon mask tool is used to select an appropriate shape for the shelf top, one that vanishes to the same point as the other side. The new shape can be filled with the same gradient that was used to fill the end cap. This process must be repeated for each of the four missing shelves. Obviously these layers should be sent to the bottom of the layer stack so they don't overlap anything.